Selenium bioaccumulation by the water boatman Trichocorixa reticulata (Guerin-Meneville)

The input of selenium from subsurface agricultural drainage into surface water systems can result in the accumulation of toxic concentrations of selenium in aquatic food chains. Elevated selenium concentrations in aquatic systems is a significant environmental problem in many areas of the United States. A laboratory investigation was conducted to determine the dominant route of selenium bioaccumulation by the corixid Trichocorixa reticulata, an important food chain organism. The roles of waterborne and foodborne exposure in selenium bioaccumulation were examined using 48-h bioassays. Waterborne selenium concentrations ranged from 0 to 1,000 microgram Se/L as selenate. A mixture of two species of blue-green algae cultured in media with selenium concentrations ranging from 0 to 1,000 microgram Se/L as selenate was used as a corixid diet in the foodborne treatments. Corixids exposed to waterborne selenate did not accumulate selenium above control concentrations. Corixids fed algae exposed to >/=100 microgram Se/L as selenate had significantly higher selenium concentrations than control organisms. These data suggest that corixids may be effectively isolated from the water and selenium accumulation is solely through dietary exposure.